plug heat range, and timing

[Mike Larson]

Hey guys... one for the engine gurus...... article in the question forum of the airplane mags caught my eye, and brought ideas and pertaining questions to mind.....

Catalytic action, from the methanol and the platinum element, as well as engine heat, keep the plug glowing once lit with the starting battery...... leaning makes it glow brighter, advancing the ignition point, while richer glows less retarding the timing....... following questions?

1. Granted a too lean condition will over glow the plug and burn out the element, assumed an advanced timing along with this...... is this the reason we run the coldest plug available, Mc 9 in my case, to try and retard and prevent an overadvanced timing scenario? ( pre det?)

2. Airplanes run lower nitro content by far, along with little or no advances internally on engine timing, comp ratio etc, would they not then so benefit running the hotter plugs pertaining to the lower nitro less explosive mixture than we do?

3. Higher nitro mixtures run cooler engine temperatures, would we not benefit from using a hotter range plug, why does the higher nitro, need to have a colder plug, and hence the ignition be retarded... ( I feel retarded)........

4. Could, measuring the EGT's of the motor, effectively tell you in any way what range of plug your motor would be suited for? is there anyone with data on the line between one range of plug and another, all else being equal, say, i'm getting Det, on Mc'9's....... you cant go any colder, and search for other options/causes?.......

5. We run water restriction, to further yet instill more motor heat, stated above, a factor involved, in the ignition of the mixture, consequently, if running the motor cooler retards the timing,(less glow) a hotter motor will have advanced timing,(more glow) and possible plug damage at some point?

Point of exercise being, with the great range of plugs on the market, getting into the "I run Mc9's club" could be great, except for I'd like to actually optimize the plug heat range my motors like and enjoy tearing them down to find nice piston tops, and a clean burn........

Any info, tech data around, or, just inspect the plug alot, like I do?...... how if at all, can it be measured, listening for a four cycle dont count....... to find the right ignition point, range of plug, you need to optimize your motor's performance?

Granted, pipe prop, fuel, and tune all combine to achieve the goal, at least being comfortable youre close on igniton, would be a good goal indeed.......

Throwin it out there......... thanks for your time.... Mike

 

[LH7018]

I don't remember where I found this article, but go here in my gallery for the article in Word document format that may answer some of your questions.

 

[Terry Keeley]

Lots of Q's there Mike but from my personal experience I like to run as hot a plug as possible and not have it go through the engine when running slightly on the rich side of center. :wacko:

It also has to last 6 laps or a couple of passes if it's R/T season.

The hotter the plug the better the idle, midrange and ability to "hit the pipe"...

I like HP's lately and have used 1L's for my 21's but find it easier to get the effect of a hotter plug other ways, it all works together as you mentioned.

One thing I can add from personal testing is that with O'Donnell plugs you can get quite over center on the needle and not put an element through the motor...

 

[Sean Bowf]

I did a very non-scientific test on glow plugs...I got a hand full of different brands and models, and tried them all one after the other, while running 40% nitro. Here was the results I got on a GPS....

#8 41.1 MPH

MC59 40.2

A5 39.1

OS99 40.5 (O'Donnell's plug I think)

MC9 39.1

Second run

#8 42

MC9 39

OS99 41.9

MC59 39.1

Sean

 

[Mike Larson]

thanks guys..... LH.... the article was informative, and yet also posed questions for further testing.....

with the range/proportion of methanol in the fuel being the key element, possible home mixing of test fuels may be in order.....

searching for the balance between possible exact engine temperature regulation to ease the effect of the platinum in the coil degenerating..... ... possibly a bigger coil surface area to help with a hotter engine, etc......

If, the methanol percentage is the overall main factor, which ingredient increases or decreases to help aleviate undue stress on the element?

Hotter engine, coldest plug, but will pushing more or less water factor in?,,, optimum engine temps?

I run turbo plugs in my modded nova's..... i've run the range from an 8, very cold to the 7's and 6's.... stated medium to cold..... these plugs are very tough, ( i've rarely gone through a pair a season) and they dont "read" as easily, as a standard mc 9, or Kb, when they burn , they just burn, with possible danger of engine damage, det, and sucking a coil.....

Granted, the little motors will accept any one from the 6 to the 8, and the performance has no noticable difference, all else being equal for the day..... which one could/should be the optimum plug for the motor, and what factors should be looked at to find out?

While the "slightly frosted" coil is one of the signs I look for, I noticed, in the article, sagging when the voltage is removed, is a sign,,,,,, pushing 3 to 5 volts to heat a turbo plug glowing, noticing surely, that, the motors will hard start if, the voltage isnt there.... ie: use a warmer plug? more methanol?.... i've heard say a little propylene?.......

While sufficing novice experience, here.... running high perf motors optimizing an easy to start, mechanically comfortable engine, is certainly what everyone looks for...... I apprecite your input........ thanks!......

 

[Richard Dahlheimer]

thanks guys..... LH.... the article was informative, and yet also posed questions for further testing..... with the range/proportion of methanol in the fuel being the key element, possible home mixing of test fuels may be in order.....

searching for the balance between possible exact engine temperature regulation to ease the effect of the platinum in the coil degenerating..... ... possibly a bigger coil surface area to help with a hotter engine, etc......

If, the methanol percentage is the overall main factor, which ingredient increases or decreases to help aleviate undue stress on the element?

Hotter engine, coldest plug, but will pushing more or less water factor in?,,, optimum engine temps?

I run turbo plugs in my modded nova's..... i've run the range from an 8, very cold to the 7's and 6's.... stated medium to cold..... these plugs are very tough, ( i've rarely gone through a pair a season) and they dont "read" as easily, as a standard mc 9, or Kb, when they burn , they just burn, with possible danger of engine damage, det, and sucking a coil.....

Granted, the little motors will accept any one from the 6 to the 8, and the performance has no noticable difference, all else being equal for the day..... which one could/should be the optimum plug for the motor, and what factors should be looked at to find out?

While the "slightly frosted" coil is one of the signs I look for, I noticed, in the article, sagging when the voltage is removed, is a sign,,,,,, pushing 3 to 5 volts to heat a turbo plug glowing, noticing surely, that, the motors will hard start if, the voltage isnt there.... ie: use a warmer plug? more methanol?.... i've heard say a little propylene?.......

While sufficing novice experience, here.... running high perf motors optimizing an easy to start, mechanically comfortable engine, is certainly what everyone looks for...... I apprecite your input........ thanks!......

I also use turbo plugs in my .21 motors. RB Concept, Novarossi and CMB. Plug of choice is short body #6. I use a power panel with its own 12volt battery just for the glow. Starting set-up has its own batteries. With the power panel, you can easily adjust the heat. Horizon sells a nice plug clip that grips turbo plugs, without having to hold it on the plug. Hope this helps. Richard D